The present invention relates to an improvement in a process for preparing basic copper carbonate (malachite), and, more particularly, to an improvement in a process for preparing agglomerates of spheroidal malachite crystals on a commercial scale.
1,4-butynediol is made according to one commercial process by reacting acetylene with formaldehyde using a copper acetylide catalyst as described in more detail in U.S. Pat. No. 4,110,249. The catalyst is described therein as being made by reacting malachite, in the form of spheroidal crystals containing bismuth oxy-compounds to suppress cuprene formation, with acetylene and formaldehyde.
U.S. Pat. Nos. 4,536,491 and 4,584,418 describe the addition of silicic acid to the malachite preparation which results in an improved agglomerated form of spheroidal malachite crystals leading to copper acetylide catalyst which filters easily and is more active. Consistently good results had been obtained on a laboratory scale using this technology, but major difficulties were encountered in trying to implement the technology to make agglomerated spheroidal malachite crystals on a large commercial scale, e.g., activity of the resulting catalyst was low, spheroidal crystals could not be consistently reproduced, and the silicic acid in the solution of the copper and bismuth salts tended to polymerize or separate and thereby become less effective if not consumed within a short time of preparation.